/**
 * 36. 有效的数独
 * https://leetcode.cn/problems/valid-sudoku/description/
 */
class Solution1 {
    boolean[][] row, col;
    boolean[][][] grid;
    public boolean isValidSudoku(char[][] board) {
        row = new boolean[9][10];
        col = new boolean[9][10];
        grid = new boolean[3][3][10];

        for(int i = 0; i < 9; i++) {
            for(int j = 0; j < 9; j++) {
                if(board[i][j] != '.') {
                    int num = board[i][j] - '0';
                    if(row[i][num] || col[j][num] || grid[i / 3][j / 3][num]) {
                        return false;
                    }
                    row[i][num] = col[j][num] = grid[i / 3][j / 3][num] = true;
                }
            }
        }
        return true;
    }
}